The present invention relates generally to a mechanical filter gauge for determining the filtering capability of a vehicle filter. Specifically, the present invention relates to a mechanical gauge for measuring the functionality of a vehicle's air filter and providing a related electrical signal at an output.
Air filter restriction gauges are used in connection with an air filter for internal combustion engines. These devices typically sense the level of airflow restriction, and then indicate the level of restriction by locking itself in position. When the air filter has become so loaded with contaminants that the supply of air required by the engine for its operating efficiency is not being drawn through the filter, the gauge will indicate this and thus alert the operator that the filter requires cleaning or replacement. Some existing devices also lock themselves in various positions to provide a continuous indication as to how much useful life remains in the air filter before it should be cleaned or changed.
The use of a gauge to monitor the filtering ability of a vehicle's air filter is known in the art. Earlier patents in this area include U.S. Pat. No. 4,369,728, issued to Nelson on Jan. 25, 1983, and U.S. Pat. No. 4,445,456, issued to Nelson on May 1, 1984. These devices provided a visual display to the users or maintenance personnel. They did not have provisions to output an electrical signal indicative of the gauge's status.
By including an electrical component to the gauge, an indicator light within the cab of the vehicle can be added. The electrical component can simply be a switch which opens or closes when predetermined conditions are met. A dashboard indicator light could then be switched appropriately. However, the signal in the vehicle and the gauge near the engine would not always agree with each other using these prior art devices. Further, the dashboard light would not always remain on until the filter was serviced and the gauge reset. Also, as disclosed, these switches were relatively expensive to manufacture and assemble. The dashboard light signal could sometimes light before the gauge actually reached "redline," or the point at which the air filter required replacement. Further, the dashboard light signal could flicker or not remain lit after the gauge had reached redline. The mere presence of the gauge and dashboard indicator will in most cases cause the driver of the vehicle to rely on the signal being given. However, if a signal is unclear, or gives a false indication that the filter is not yet in need of replacement, serious engine damage could result.
Once a clean and predictable signal could be developed as an output from the gauge, this signal could also be input to a computer control system or system controller to coordinate many functions. For example, this could provide an indication of an engine's operating conditions.
As mentioned above, several air filter restriction indicator gauges have been available for quite some time. Initially, these indicator gauges were simply a single stage type gauge where a warning button would pop once a predetermined restriction level was achieved. These gauges were phased out in favor of the incremental type gauges. The pop-up type gauges were not believed to be reliable and typically not trusted. The incremental type gauges would display an indication of the amount of filter left, thus would provide more reliable and believable information to the users. However, again as mentioned, none of these incremental gauges included reliable switching indicators which could be used to generate displays or to feed a system controller. If input to the system controller, even a single stage gauge is valuable as this provides meaningful information to the controller. Further, even a gauge which does not lock after predetermined levels nor requires manual resetting is provided, beneficial information can be measured and tracked.
Additionally, prior art indicators have not always been easy to fully reset, sometimes resulting in a gauge that may give a false, premature signal that an air filter requires replacement. This may in turn result in unnecessary filter maintenance.